Multi-level configuration and optimization of a thermal energy storage system using a metal hydride pair

Metal hydride thermal energy storage (TES) system is an attractive option for the concentrated solar power. In this article, a multi-level configuration is proposed to intensify the discharging process of TES system using MgH2/LaNi5 pair. The discharging process is simulated by establishing a mathematical model, which is solved by COMSOL Multiphysics v5.1. The multi-layer structure of storage units is simplified by the conversion of porosity and thermal conductivity. It is found that the multi-level configuration mitigates the non-uniform reaction along the oil flow direction so as to enhance the overall discharging performance effectively, such as the decrease of discharging time from 17,350 s to 14,688 s and the increase of output temperature by ∼5 °C. Meanwhile, the optimum number of levels is determined between 4 and 5 according to the effect of the number of levels on the discharging performance. Furthermore, it is revealed that the optimum allocation principle of storage materials is to maintain the same discharging time for all the subsystems.